Which set correctly pairs a vitamin with one of its primary biochemical roles?

Vitamin A — required exclusively for sodium–potassium pump ion balance in cells; Vitamin C — signaling hormone identical to steroid hormones; Niacin — major constituent of teeth and bone.

Niacin (B3) — enzyme cofactor; Vitamin D — signaling molecule for calcium handling; Vitamin C — antioxidant.

Folate — fat-soluble storage vitamin; Vitamin D — water-soluble antioxidant; Vitamin B6 — mineral that contributes to bone rigidity.

Vitamin K — antioxidant; Vitamin B12 — structural component of bone mineral; Vitamin E — enzyme cofactor for glycolysis.